The study found that 99 of 139 samples contained species not declared on the product label, with the highest incidence in sausages, burgers and deli meats. Photograph: Niall Carson/PA

South African food scientists say there is water buffalo, donkey and goat meat in mislabelled South African foods including beefburgers and sausages.

A study published by three professors at Stellenbosch University found that 99 of 139 samples contained species not declared on the product label, with the highest incidence in sausages, burgers and deli meats.

The study found soya and gluten were not labelled in 28% of products tested, undeclared pork in 37% and chicken in 23%.

Co-author Professor Louwrens C Hoffman said: "This study confirms that the mislabelling of processed meats is commonplace in South Africa and not only violates food labelling regulations but also poses economic, religious, ethical and health impacts."